Sanitary considerations in production of food and beverage products are of critical importance. Plants must meet hygienic engineering and food safety standards to avoid product’s degradation and contamination, which can occur during processing operations due to insufficient cleaning of processing equipment which are exposed to product, and therefore plant cleaning must be carried out quickly and thoroughly. Cleaning requirements are best met with Clean-in-Place (CIP) systems, which is very well established technique used in various bio-pharma and food industries.
Basically, CIP refers to all those mechanical and chemical systems that are necessary to prepare equipment or pipeline circuits for food processing, either after a processing run that has produced fouling or when switching a processing line from one recipe to another. CIP is done without dismantling or opening the system, leading to less production downtime. On a daily basis, huge numbers of small and large vessels need to be cleaned in an economical, efficient and reproducible manner. To achieve this, spray balls play an integral role as a component of overall CIP System to assure product safety.
CIP of pipelines is relatively easier and yield more efficiency due to the turbulence caused in pipeline during cleaning but for tanks or vessels of high capacity or large build, simply pumping of detergents or liquid are not of much help as corners remains uncleaned. Spray balls are the cleaning nozzles used for efficient cleaning of tanks, vessels and other containers of various shapes and sizes where cleaning solution cannot be reached. Water when confined its flow through small nozzles is pressurized and cleans surfaces effectively. Because of its sanitary design it is widely used in breweries, dairies and other food industries as well as in pharmaceutical and chemical applications where manual cleaning is not possible to avoid human caused error in cleaning and to reduce the downtime of the process.
Spray balls have numerous small holes, perforated partially or completely on its surface. It facilitates the efficient cleaning of process equipment by drenching the interior surfaces of the vessels with hot water and cleaning solutions at various velocities, thus making them suitable for CIP. Spray balls offer basic rinsing of the tank’s internal surface where each hole acts as a divergent spray which have whirling effect for removing soil in a turbulent way. Spray balls ensure that the process of cleaning is highly effective and it can be designed and automated to allow for maximum coverage. Several factors are need to be considered during cleaning process like coverage of the spray balls.
Types of Spay Balls
Based on the mode of operation spray balls may be static or rotary types:
- Static Spray Ball: This particular spray ball is a permanent static mount, designed to direct multiple high-velocity jets against the tank wall which do not require more fluid. They are used primarily for rinsing tanks. They are inexpensive to purchase and are very robust.
- Rotary Spray Ball: The cleaning fluid drives the spray head by means of specially positioned nozzles. The rapidly repeated impacts remove the soil and rinses it from tank surfaces. This results in optimum cleaning efficiency at low pressure in small to large sized tanks.
Construction of Spray Balls
A spray ball consists of three parts
- Hollow sphere which is partially or completely covered with tiny holes perforated inside it.
- A long or small connecting rod for its attachment to pipe fittings of containment for supplying liquid and chemicals
- Bearing which may be present or absent depending on its operation
Material for construction is selected in such a way that it offers high resistance against cleaning chemicals and temperature variations. Therefore, spray ball used in food industries are mostly made up of SS 316L/304L, PTFE, PVDF which can be personalized according to process specifications. Moreover, material chosen must be food grade and comply with the requirements of regulatory bodies.
Features for Selection
- Extent of Cleaning: The nature of substance to be cleaned from tank should be considered like, solubility, viscosity, nature of powder / pigment material.
- Pump and Pipes: The pipe size used depends mainly on the required flow rate and should be chosen so that the pressure losses in the pipe system are as low as possible. It must be guaranteed that required static operating pressure is available directly at the nozzle. The pump power must be matched to this.
- Arrangement: The nozzles must be positioned in the upper part of the tank where possible. In addition, it must be ensured that sufficient cleaning fluid strikes the tank top.
- Filling Level: If possible, the nozzle should not come into contact with the product during production. The nozzle should be positioned above the maximum product level in the tank.
- Tank Drainage Rate: The tank drainage rate is to be selected to prevent the level of liquid from rising during the cleaning process. Make sure the drain can handle whatever volume you put into tank.
- Elimination of Shadowing Effect: Obstructions in the vessel such as agitators or baffles can cause “shadowing” of areas where spray cannot reach which greatly reduces the cleaning efficacy of a single spray ball. In these cases, two or more nozzles may be required to effectively clean the entire vessel.
- Drill Pattern: Spray ball drill patterns depend on a spray ball’s placement, surface area coverage requirements, and obstructions. Standard spray ball patterns ranges from 90 to 360-degree coverage.
- Ball Diameter: Ball diameters typically range from 1.25″ to 4″.
- Connection Size: Connection size may range from 0.5″ to 2.5″, which determines the maximum flow delivered through a spray ball with acceptable pressure drops.
- Connection Style. A slip collar is a standard connection. Other connection styles include butt weld, flare (no connection), tri-clamp, half coupling, and pipe nipple.
- Flow: A minimum flow rate of three gallon per minutes for every foot of tank circumference is required to provide enough flow for cleaning coverage. Increase in flow rate by using larger nozzle increases the impact assuming that other parameters remain same.
- Pressure: 25 psi is the standard design flow rate if not specified by the user with maximum pressure for custom spray balls being 70 psi. With rotating nozzles, the supply pressure normally influences the rotation speed. Higher the rotation speed, greater is the tendency of rotating nozzles to atomize the fluid into much smaller droplets.
Spray ball must have provision of drain hole to guarantee the complete drainage of the cleaning/rinsing solution. Its absence may lead to creation of dead spaces which may lead to corrosion (rogue) of stainless steel. Surfaces of spray ball must be grounded or electropolished for lowering the surface roughness (0.8 Ra) in order to meet hygienic requirement. Spray ball may be thin walled and thick walled based on the thickness of the hollow sphere. But thin walled spray balls cannot withstand high pressure of flow stream. This disadvantage can be overcome by using thick walled spray ball which is designed to withstand high impact and in this each hole acts as a very efficient cleaning jet.